Abstract:

Pasture-based dairies utilize a major strength of livestock production in the Southeastern US – the ability to produce quality forages during the majority of the calendar year. Pasture-based systems use irrigation to enhance forage production. However, little information exists on the fate of nitrogen and its impact on ground water quality, or on irrigated forage productivity when intensively grazed. The objectives of this study were to: 1) Screen warm and cool-season annual and perennial pasture species for seasonal forage productivity under grazing conditions, 2) monitor soil moisture content from irrigation practices to determine efficiency of irrigation practices, 3) Create a nitrogen “budget” to determine nitrogen losses, and 4) Develop educational and outreach information for training producers to be more efficient at, or transition into, pasture-based dairying. Research was conducted on two commercial farms located in the Coastal Plain of Georgia. Perennial forages were no-till established in paddock areas following herbicide application, and winter annual forages were no-till established as a double crop in bermudagrass paddocks. Soil moisture was measured electronically and irrigation efficiency was determined on two center pivots on each farm: one in which computer generated data was used to indicate irrigation needs and one in which producers used established irrigation practices. Nitrogen inputs were calculated from farm records and N losses calculated from nitrate efflux in soil water and ammonia losses measured in traps and PVC chambers. Data was used to supplement educational efforts specifically designed for pasture-based dairies.
The best pasture mixtures for year around forage production was a combination of bermudagrass overseeded with combinations of cereal rye, ryegrass, and crimson clover. Lack of participation on the part by producers did not permit assessment of irrigation efficiency at either farm. Lack of participation was a result of prioritization of other farm enterprises over irrigation management. Ammonia volatilization losses amounted to 2% and 1%; and leached nitrate, amounted to 12.5 and 0.3% of the total imported N from the two farms. UGA has held three intensive grazing management schools since 2008. One hundred and seven producers (representing 72 farms) in attended. We also conducted a comprehensive training for 108 Extension Agents, NRCS personnel, State Dept. of Ag officials, and other agricultural professionals from 8 states in SSARE’s region. The number of dairy cows on pasture-based dairies at the onset of this research project was less than 1% of the Georgia state herd, but in 2010 dairy cows on pasture-based dairies was approximately 15% of the Georgia herd and increasing at an exponential rate.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.

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